CityApper
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django
kopia lustrzana https://github.com/django/django


			
				
					
						
						
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							=============
Testing tools
=============

.. currentmodule:: django.test

Django provides a small set of tools that come in handy when writing tests.

.. _test-client:

The test client
---------------

The test client is a Python class that acts as a dummy Web browser, allowing
you to test your views and interact with your Django-powered application
programmatically.

Some of the things you can do with the test client are:

* Simulate GET and POST requests on a URL and observe the response --
  everything from low-level HTTP (result headers and status codes) to
  page content.

* See the chain of redirects (if any) and check the URL and status code at
  each step.

* Test that a given request is rendered by a given Django template, with
  a template context that contains certain values.

Note that the test client is not intended to be a replacement for Selenium_ or
other "in-browser" frameworks. Django's test client has a different focus. In
short:

* Use Django's test client to establish that the correct template is being
  rendered and that the template is passed the correct context data.

* Use in-browser frameworks like Selenium_ to test *rendered* HTML and the
  *behavior* of Web pages, namely JavaScript functionality. Django also
  provides special support for those frameworks; see the section on
  :class:`~django.test.LiveServerTestCase` for more details.

A comprehensive test suite should use a combination of both test types.

Overview and a quick example
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To use the test client, instantiate ``django.test.Client`` and retrieve
Web pages::

    >>> from django.test import Client
    >>> c = Client()
    >>> response = c.post('/login/', {'username': 'john', 'password': 'smith'})
    >>> response.status_code
    200
    >>> response = c.get('/customer/details/')
    >>> response.content
    '<!DOCTYPE html...'

As this example suggests, you can instantiate ``Client`` from within a session
of the Python interactive interpreter.

Note a few important things about how the test client works:

* The test client does *not* require the Web server to be running. In fact,
  it will run just fine with no Web server running at all! That's because
  it avoids the overhead of HTTP and deals directly with the Django
  framework. This helps make the unit tests run quickly.

* When retrieving pages, remember to specify the *path* of the URL, not the
  whole domain. For example, this is correct::

      >>> c.get('/login/')

  This is incorrect::

      >>> c.get('http://www.example.com/login/')

  The test client is not capable of retrieving Web pages that are not
  powered by your Django project. If you need to retrieve other Web pages,
  use a Python standard library module such as :mod:`urllib` or
  :mod:`urllib2`.

* To resolve URLs, the test client uses whatever URLconf is pointed-to by
  your :setting:`ROOT_URLCONF` setting.

* Although the above example would work in the Python interactive
  interpreter, some of the test client's functionality, notably the
  template-related functionality, is only available *while tests are
  running*.

  The reason for this is that Django's test runner performs a bit of black
  magic in order to determine which template was loaded by a given view.
  This black magic (essentially a patching of Django's template system in
  memory) only happens during test running.

* By default, the test client will disable any CSRF checks
  performed by your site.

  If, for some reason, you *want* the test client to perform CSRF
  checks, you can create an instance of the test client that
  enforces CSRF checks. To do this, pass in the
  ``enforce_csrf_checks`` argument when you construct your
  client::

      >>> from django.test import Client
      >>> csrf_client = Client(enforce_csrf_checks=True)

Making requests
~~~~~~~~~~~~~~~

Use the ``django.test.Client`` class to make requests.

.. class:: Client(enforce_csrf_checks=False, **defaults)

    It requires no arguments at time of construction. However, you can use
    keywords arguments to specify some default headers. For example, this will
    send a ``User-Agent`` HTTP header in each request::

        >>> c = Client(HTTP_USER_AGENT='Mozilla/5.0')

    The values from the ``extra`` keywords arguments passed to
    :meth:`~django.test.Client.get()`,
    :meth:`~django.test.Client.post()`, etc. have precedence over
    the defaults passed to the class constructor.

    The ``enforce_csrf_checks`` argument can be used to test CSRF
    protection (see above).

    Once you have a ``Client`` instance, you can call any of the following
    methods:

    .. method:: Client.get(path, data={}, follow=False, secure=False, **extra)

        .. versionadded:: 1.7

            The ``secure`` argument was added.

        Makes a GET request on the provided ``path`` and returns a ``Response``
        object, which is documented below.

        The key-value pairs in the ``data`` dictionary are used to create a GET
        data payload. For example::

            >>> c = Client()
            >>> c.get('/customers/details/', {'name': 'fred', 'age': 7})

        ...will result in the evaluation of a GET request equivalent to::

            /customers/details/?name=fred&age=7

        The ``extra`` keyword arguments parameter can be used to specify
        headers to be sent in the request. For example::

            >>> c = Client()
            >>> c.get('/customers/details/', {'name': 'fred', 'age': 7},
            ...       HTTP_X_REQUESTED_WITH='XMLHttpRequest')

        ...will send the HTTP header ``HTTP_X_REQUESTED_WITH`` to the
        details view, which is a good way to test code paths that use the
        :meth:`django.http.HttpRequest.is_ajax()` method.

        .. admonition:: CGI specification

            The headers sent via ``**extra`` should follow CGI_ specification.
            For example, emulating a different "Host" header as sent in the
            HTTP request from the browser to the server should be passed
            as ``HTTP_HOST``.

            .. _CGI: http://www.w3.org/CGI/

        If you already have the GET arguments in URL-encoded form, you can
        use that encoding instead of using the data argument. For example,
        the previous GET request could also be posed as::

        >>> c = Client()
        >>> c.get('/customers/details/?name=fred&age=7')

        If you provide a URL with both an encoded GET data and a data argument,
        the data argument will take precedence.

        If you set ``follow`` to ``True`` the client will follow any redirects
        and a ``redirect_chain`` attribute will be set in the response object
        containing tuples of the intermediate urls and status codes.

        If you had a URL ``/redirect_me/`` that redirected to ``/next/``, that
        redirected to ``/final/``, this is what you'd see::

            >>> response = c.get('/redirect_me/', follow=True)
            >>> response.redirect_chain
            [(u'http://testserver/next/', 302), (u'http://testserver/final/', 302)]

        If you set ``secure`` to ``True`` the client will emulate an HTTPS
        request.

    .. method:: Client.post(path, data={}, content_type=MULTIPART_CONTENT, follow=False, secure=False, **extra)

        Makes a POST request on the provided ``path`` and returns a
        ``Response`` object, which is documented below.

        The key-value pairs in the ``data`` dictionary are used to submit POST
        data. For example::

            >>> c = Client()
            >>> c.post('/login/', {'name': 'fred', 'passwd': 'secret'})

        ...will result in the evaluation of a POST request to this URL::

            /login/

        ...with this POST data::

            name=fred&passwd=secret

        If you provide ``content_type`` (e.g. :mimetype:`text/xml` for an XML
        payload), the contents of ``data`` will be sent as-is in the POST
        request, using ``content_type`` in the HTTP ``Content-Type`` header.

        If you don't provide a value for ``content_type``, the values in
        ``data`` will be transmitted with a content type of
        :mimetype:`multipart/form-data`. In this case, the key-value pairs in
        ``data`` will be encoded as a multipart message and used to create the
        POST data payload.

        To submit multiple values for a given key -- for example, to specify
        the selections for a ``<select multiple>`` -- provide the values as a
        list or tuple for the required key. For example, this value of ``data``
        would submit three selected values for the field named ``choices``::

            {'choices': ('a', 'b', 'd')}

        Submitting files is a special case. To POST a file, you need only
        provide the file field name as a key, and a file handle to the file you
        wish to upload as a value. For example::

            >>> c = Client()
            >>> with open('wishlist.doc') as fp:
            ...     c.post('/customers/wishes/', {'name': 'fred', 'attachment': fp})

        (The name ``attachment`` here is not relevant; use whatever name your
        file-processing code expects.)

        Note that if you wish to use the same file handle for multiple
        ``post()`` calls then you will need to manually reset the file
        pointer between posts. The easiest way to do this is to
        manually close the file after it has been provided to
        ``post()``, as demonstrated above.

        You should also ensure that the file is opened in a way that
        allows the data to be read. If your file contains binary data
        such as an image, this means you will need to open the file in
        ``rb`` (read binary) mode.

        The ``extra`` argument acts the same as for :meth:`Client.get`.

        If the URL you request with a POST contains encoded parameters, these
        parameters will be made available in the request.GET data. For example,
        if you were to make the request::

        >>> c.post('/login/?visitor=true', {'name': 'fred', 'passwd': 'secret'})

        ... the view handling this request could interrogate request.POST
        to retrieve the username and password, and could interrogate request.GET
        to determine if the user was a visitor.

        If you set ``follow`` to ``True`` the client will follow any redirects
        and a ``redirect_chain`` attribute will be set in the response object
        containing tuples of the intermediate urls and status codes.

        If you set ``secure`` to ``True`` the client will emulate an HTTPS
        request.

    .. method:: Client.head(path, data={}, follow=False, secure=False, **extra)

        Makes a HEAD request on the provided ``path`` and returns a
        ``Response`` object. This method works just like :meth:`Client.get`,
        including the ``follow``, ``secure`` and ``extra`` arguments, except
        it does not return a message body.

    .. method:: Client.options(path, data='', content_type='application/octet-stream', follow=False, secure=False, **extra)

        Makes an OPTIONS request on the provided ``path`` and returns a
        ``Response`` object. Useful for testing RESTful interfaces.

        When ``data`` is provided, it is used as the request body, and
        a ``Content-Type`` header is set to ``content_type``.

        The ``follow``, ``secure`` and ``extra`` arguments act the same as for
        :meth:`Client.get`.

    .. method:: Client.put(path, data='', content_type='application/octet-stream', follow=False, secure=False, **extra)

        Makes a PUT request on the provided ``path`` and returns a
        ``Response`` object. Useful for testing RESTful interfaces.

        When ``data`` is provided, it is used as the request body, and
        a ``Content-Type`` header is set to ``content_type``.

        The ``follow``, ``secure`` and ``extra`` arguments act the same as for
        :meth:`Client.get`.

    .. method:: Client.patch(path, data='', content_type='application/octet-stream', follow=False, secure=False, **extra)

        Makes a PATCH request on the provided ``path`` and returns a
        ``Response`` object. Useful for testing RESTful interfaces.

        The ``follow``, ``secure`` and ``extra`` arguments act the same as for
        :meth:`Client.get`.

    .. method:: Client.delete(path, data='', content_type='application/octet-stream', follow=False, secure=False, **extra)

        Makes an DELETE request on the provided ``path`` and returns a
        ``Response`` object. Useful for testing RESTful interfaces.

        When ``data`` is provided, it is used as the request body, and
        a ``Content-Type`` header is set to ``content_type``.

        The ``follow``, ``secure`` and ``extra`` arguments act the same as for
        :meth:`Client.get`.

    .. method:: Client.login(**credentials)

        If your site uses Django's :doc:`authentication system</topics/auth/index>`
        and you deal with logging in users, you can use the test client's
        ``login()`` method to simulate the effect of a user logging into the
        site.

        After you call this method, the test client will have all the cookies
        and session data required to pass any login-based tests that may form
        part of a view.

        The format of the ``credentials`` argument depends on which
        :ref:`authentication backend <authentication-backends>` you're using
        (which is configured by your :setting:`AUTHENTICATION_BACKENDS`
        setting). If you're using the standard authentication backend provided
        by Django (``ModelBackend``), ``credentials`` should be the user's
        username and password, provided as keyword arguments::

            >>> c = Client()
            >>> c.login(username='fred', password='secret')

            # Now you can access a view that's only available to logged-in users.

        If you're using a different authentication backend, this method may
        require different credentials. It requires whichever credentials are
        required by your backend's ``authenticate()`` method.

        ``login()`` returns ``True`` if it the credentials were accepted and
        login was successful.

        Finally, you'll need to remember to create user accounts before you can
        use this method. As we explained above, the test runner is executed
        using a test database, which contains no users by default. As a result,
        user accounts that are valid on your production site will not work
        under test conditions. You'll need to create users as part of the test
        suite -- either manually (using the Django model API) or with a test
        fixture. Remember that if you want your test user to have a password,
        you can't set the user's password by setting the password attribute
        directly -- you must use the
        :meth:`~django.contrib.auth.models.User.set_password()` function to
        store a correctly hashed password. Alternatively, you can use the
        :meth:`~django.contrib.auth.models.UserManager.create_user` helper
        method to create a new user with a correctly hashed password.

        .. versionadded:: 1.7

            Requests made with :meth:`~django.test.Client.login` go through the
            request middleware. If you need to control the environment, you can
            do so at :class:`~django.test.Client` instantiation or with the
            `Client.defaults` attribute.

    .. method:: Client.logout()

        If your site uses Django's :doc:`authentication system</topics/auth/index>`,
        the ``logout()`` method can be used to simulate the effect of a user
        logging out of your site.

        After you call this method, the test client will have all the cookies
        and session data cleared to defaults. Subsequent requests will appear
        to come from an :class:`~django.contrib.auth.models.AnonymousUser`.

        .. versionadded:: 1.7

            Requests made with :meth:`~django.test.Client.logout` go through the
            request middleware. If you need to control the environment, you can
            do so at :class:`~django.test.Client` instantiation or with the
            `Client.defaults` attribute.

Testing responses
~~~~~~~~~~~~~~~~~

The ``get()`` and ``post()`` methods both return a ``Response`` object. This
``Response`` object is *not* the same as the ``HttpResponse`` object returned
Django views; the test response object has some additional data useful for
test code to verify.

Specifically, a ``Response`` object has the following attributes:

.. class:: Response()

    .. attribute:: client

        The test client that was used to make the request that resulted in the
        response.

    .. attribute:: content

        The body of the response, as a string. This is the final page content as
        rendered by the view, or any error message.

    .. attribute:: context

        The template ``Context`` instance that was used to render the template that
        produced the response content.

        If the rendered page used multiple templates, then ``context`` will be a
        list of ``Context`` objects, in the order in which they were rendered.

        Regardless of the number of templates used during rendering, you can
        retrieve context values using the ``[]`` operator. For example, the
        context variable ``name`` could be retrieved using::

            >>> response = client.get('/foo/')
            >>> response.context['name']
            'Arthur'

    .. attribute:: request

        The request data that stimulated the response.

    .. attribute:: status_code

        The HTTP status of the response, as an integer. See
        :rfc:`2616#section-10` for a full list of HTTP status codes.

    .. attribute:: templates

        A list of ``Template`` instances used to render the final content, in
        the order they were rendered. For each template in the list, use
        ``template.name`` to get the template's file name, if the template was
        loaded from a file. (The name is a string such as
        ``'admin/index.html'``.)

You can also use dictionary syntax on the response object to query the value
of any settings in the HTTP headers. For example, you could determine the
content type of a response using ``response['Content-Type']``.

Exceptions
~~~~~~~~~~

If you point the test client at a view that raises an exception, that exception
will be visible in the test case. You can then use a standard ``try ... except``
block or :meth:`~unittest.TestCase.assertRaises` to test for exceptions.

The only exceptions that are not visible to the test client are ``Http404``,
``PermissionDenied`` and ``SystemExit``. Django catches these exceptions
internally and converts them into the appropriate HTTP response codes. In these
cases, you can check ``response.status_code`` in your test.

Persistent state
~~~~~~~~~~~~~~~~

The test client is stateful. If a response returns a cookie, then that cookie
will be stored in the test client and sent with all subsequent ``get()`` and
``post()`` requests.

Expiration policies for these cookies are not followed. If you want a cookie
to expire, either delete it manually or create a new ``Client`` instance (which
will effectively delete all cookies).

A test client has two attributes that store persistent state information. You
can access these properties as part of a test condition.

.. attribute:: Client.cookies

    A Python :class:`~Cookie.SimpleCookie` object, containing the current values
    of all the client cookies. See the documentation of the :mod:`Cookie` module
    for more.

.. attribute:: Client.session

    A dictionary-like object containing session information. See the
    :doc:`session documentation</topics/http/sessions>` for full details.

    To modify the session and then save it, it must be stored in a variable
    first (because a new ``SessionStore`` is created every time this property
    is accessed)::

        def test_something(self):
            session = self.client.session
            session['somekey'] = 'test'
            session.save()

Example
~~~~~~~

The following is a simple unit test using the test client::

    import unittest
    from django.test import Client

    class SimpleTest(unittest.TestCase):
        def setUp(self):
            # Every test needs a client.
            self.client = Client()

        def test_details(self):
            # Issue a GET request.
            response = self.client.get('/customer/details/')

            # Check that the response is 200 OK.
            self.assertEqual(response.status_code, 200)

            # Check that the rendered context contains 5 customers.
            self.assertEqual(len(response.context['customers']), 5)

.. seealso::

    :class:`django.test.RequestFactory`

.. _django-testcase-subclasses:

Provided test case classes
--------------------------

Normal Python unit test classes extend a base class of
:class:`unittest.TestCase`. Django provides a few extensions of this base class:

.. _testcase_hierarchy_diagram:

.. figure:: _images/django_unittest_classes_hierarchy.*
   :alt: Hierarchy of Django unit testing classes (TestCase subclasses)
   :width: 508
   :height: 328

   Hierarchy of Django unit testing classes

SimpleTestCase
~~~~~~~~~~~~~~

.. class:: SimpleTestCase()

A thin subclass of :class:`unittest.TestCase`, it extends it with some basic
functionality like:

* Saving and restoring the Python warning machinery state.
* Some useful assertions like:

  * Checking that a callable :meth:`raises a certain exception
    <SimpleTestCase.assertRaisesMessage>`.
  * Testing form field :meth:`rendering and error treatment
    <SimpleTestCase.assertFieldOutput>`.
  * Testing :meth:`HTML responses for the presence/lack of a given fragment
    <SimpleTestCase.assertContains>`.
  * Verifying that a template :meth:`has/hasn't been used to generate a given
    response content <SimpleTestCase.assertTemplateUsed>`.
  * Verifying a HTTP :meth:`redirect <SimpleTestCase.assertRedirects>` is
    performed by the app.
  * Robustly testing two :meth:`HTML fragments <SimpleTestCase.assertHTMLEqual>`
    for equality/inequality or :meth:`containment <SimpleTestCase.assertInHTML>`.
  * Robustly testing two :meth:`XML fragments <SimpleTestCase.assertXMLEqual>`
    for equality/inequality.
  * Robustly testing two :meth:`JSON fragments <SimpleTestCase.assertJSONEqual>`
    for equality.

* The ability to run tests with :ref:`modified settings <overriding-settings>`.
* Using the :attr:`~SimpleTestCase.client` :class:`~django.test.Client`.
* Custom test-time :attr:`URL maps <SimpleTestCase.urls>`.

.. versionchanged:: 1.6

    The latter two features were moved from ``TransactionTestCase`` to
    ``SimpleTestCase`` in Django 1.6.

If you need any of the other more complex and heavyweight Django-specific
features like:

* Testing or using the ORM.
* Database :attr:`~TransactionTestCase.fixtures`.
* Test :ref:`skipping based on database backend features <skipping-tests>`.
* The remaining specialized :meth:`assert*
  <TransactionTestCase.assertQuerysetEqual>` methods.

then you should use :class:`~django.test.TransactionTestCase` or
:class:`~django.test.TestCase` instead.

``SimpleTestCase`` inherits from ``unittest.TestCase``.

TransactionTestCase
~~~~~~~~~~~~~~~~~~~

.. class:: TransactionTestCase()

Django's ``TestCase`` class (described below) makes use of database transaction
facilities to speed up the process of resetting the database to a known state
at the beginning of each test. A consequence of this, however, is that the
effects of transaction commit and rollback cannot be tested by a Django
``TestCase`` class. If your test requires testing of such transactional
behavior, you should use a Django ``TransactionTestCase``.

``TransactionTestCase`` and ``TestCase`` are identical except for the manner
in which the database is reset to a known state and the ability for test code
to test the effects of commit and rollback:

* A ``TransactionTestCase`` resets the database after the test runs by
  truncating all tables. A ``TransactionTestCase`` may call commit and rollback
  and observe the effects of these calls on the database.

* A ``TestCase``, on the other hand, does not truncate tables after a test.
  Instead, it encloses the test code in a database transaction that is rolled
  back at the end of the test. Both explicit commits like
  ``transaction.commit()`` and implicit ones that may be caused by
  ``transaction.atomic()`` are replaced with a ``nop`` operation. This
  guarantees that the rollback at the end of the test restores the database to
  its initial state.

  When running on a database that does not support rollback (e.g. MySQL with the
  MyISAM storage engine), ``TestCase`` falls back to initializing the database
  by truncating tables and reloading initial data.

.. warning::

    While ``commit`` and ``rollback`` operations still *appear* to work when
    used in ``TestCase``, no actual commit or rollback will be performed by the
    database. This can cause your tests to pass or fail unexpectedly. Always
    use ``TransactionTestCase`` when testing transactional behavior.

``TransactionTestCase`` inherits from :class:`~django.test.SimpleTestCase`.

TestCase
~~~~~~~~

.. class:: TestCase()

This class provides some additional capabilities that can be useful for testing
Web sites.

Converting a normal :class:`unittest.TestCase` to a Django :class:`TestCase` is
easy: Just change the base class of your test from ``'unittest.TestCase'`` to
``'django.test.TestCase'``. All of the standard Python unit test functionality
will continue to be available, but it will be augmented with some useful
additions, including:

* Automatic loading of fixtures.

* Wraps each test in a transaction.

* Creates a TestClient instance.

* Django-specific assertions for testing for things like redirection and form
  errors.

``TestCase`` inherits from :class:`~django.test.TransactionTestCase`.

.. _live-test-server:

LiveServerTestCase
~~~~~~~~~~~~~~~~~~

.. class:: LiveServerTestCase()

``LiveServerTestCase`` does basically the same as
:class:`~django.test.TransactionTestCase` with one extra feature: it launches a
live Django server in the background on setup, and shuts it down on teardown.
This allows the use of automated test clients other than the
:ref:`Django dummy client <test-client>` such as, for example, the Selenium_
client, to execute a series of functional tests inside a browser and simulate a
real user's actions.

By default the live server's address is ``'localhost:8081'`` and the full URL
can be accessed during the tests with ``self.live_server_url``. If you'd like
to change the default address (in the case, for example, where the 8081 port is
already taken) then you may pass a different one to the :djadmin:`test` command
via the :djadminopt:`--liveserver` option, for example:

.. code-block:: bash

    ./manage.py test --liveserver=localhost:8082

Another way of changing the default server address is by setting the
`DJANGO_LIVE_TEST_SERVER_ADDRESS` environment variable somewhere in your
code (for example, in a :ref:`custom test runner<topics-testing-test_runner>`):

.. code-block:: python

    import os
    os.environ['DJANGO_LIVE_TEST_SERVER_ADDRESS'] = 'localhost:8082'

In the case where the tests are run by multiple processes in parallel (for
example, in the context of several simultaneous `continuous integration`_
builds), the processes will compete for the same address, and therefore your
tests might randomly fail with an "Address already in use" error. To avoid this
problem, you can pass a comma-separated list of ports or ranges of ports (at
least as many as the number of potential parallel processes). For example:

.. code-block:: bash

    ./manage.py test --liveserver=localhost:8082,8090-8100,9000-9200,7041

Then, during test execution, each new live test server will try every specified
port until it finds one that is free and takes it.

.. _continuous integration: http://en.wikipedia.org/wiki/Continuous_integration

To demonstrate how to use ``LiveServerTestCase``, let's write a simple Selenium
test. First of all, you need to install the `selenium package`_ into your
Python path:

.. code-block:: bash

   pip install selenium

Then, add a ``LiveServerTestCase``-based test to your app's tests module
(for example: ``myapp/tests.py``). The code for this test may look as follows:

.. code-block:: python

    from django.test import LiveServerTestCase
    from selenium.webdriver.firefox.webdriver import WebDriver

    class MySeleniumTests(LiveServerTestCase):
        fixtures = ['user-data.json']

        @classmethod
        def setUpClass(cls):
            cls.selenium = WebDriver()
            super(MySeleniumTests, cls).setUpClass()

        @classmethod
        def tearDownClass(cls):
            cls.selenium.quit()
            super(MySeleniumTests, cls).tearDownClass()

        def test_login(self):
            self.selenium.get('%s%s' % (self.live_server_url, '/login/'))
            username_input = self.selenium.find_element_by_name("username")
            username_input.send_keys('myuser')
            password_input = self.selenium.find_element_by_name("password")
            password_input.send_keys('secret')
            self.selenium.find_element_by_xpath('//input[@value="Log in"]').click()

Finally, you may run the test as follows:

.. code-block:: bash

    ./manage.py test myapp.MySeleniumTests.test_login

This example will automatically open Firefox then go to the login page, enter
the credentials and press the "Log in" button. Selenium offers other drivers in
case you do not have Firefox installed or wish to use another browser. The
example above is just a tiny fraction of what the Selenium client can do; check
out the `full reference`_ for more details.

.. _Selenium: http://seleniumhq.org/
.. _selenium package: https://pypi.python.org/pypi/selenium
.. _full reference: http://selenium-python.readthedocs.org/en/latest/api.html
.. _Firefox: http://www.mozilla.com/firefox/

.. versionchanged:: 1.7

    Before Django 1.7 ``LiveServerTestCase`` used to rely on the
    :doc:`staticfiles contrib app </howto/static-files/index>` to get the
    static assets of the application(s) under test transparently served at their
    expected locations during the execution of these tests.

    In Django 1.7 this dependency of core functionality on a ``contrib``
    appplication has been removed, because of which ``LiveServerTestCase``
    ability in this respect has been retrofitted to simply publish the contents
    of the file system under :setting:`STATIC_ROOT` at the :setting:`STATIC_URL`
    URL.

    If you use the ``staticfiles`` app in your project and need to perform live
    testing then you might want to consider using the
    :class:`~django.contrib.staticfiles.testing.StaticLiveServerCase` subclass
    shipped with it instead because it's the one that implements the original
    behavior now. See :ref:`the relevant documentation
    <staticfiles-testing-support>` for more details.

.. note::

    When using an in-memory SQLite database to run the tests, the same database
    connection will be shared by two threads in parallel: the thread in which
    the live server is run and the thread in which the test case is run. It's
    important to prevent simultaneous database queries via this shared
    connection by the two threads, as that may sometimes randomly cause the
    tests to fail. So you need to ensure that the two threads don't access the
    database at the same time. In particular, this means that in some cases
    (for example, just after clicking a link or submitting a form), you might
    need to check that a response is received by Selenium and that the next
    page is loaded before proceeding with further test execution.
    Do this, for example, by making Selenium wait until the ``<body>`` HTML tag
    is found in the response (requires Selenium > 2.13):

    .. code-block:: python

        def test_login(self):
            from selenium.webdriver.support.wait import WebDriverWait
            timeout = 2
            ...
            self.selenium.find_element_by_xpath('//input[@value="Log in"]').click()
            # Wait until the response is received
            WebDriverWait(self.selenium, timeout).until(
                lambda driver: driver.find_element_by_tag_name('body'))

    The tricky thing here is that there's really no such thing as a "page load,"
    especially in modern Web apps that generate HTML dynamically after the
    server generates the initial document. So, simply checking for the presence
    of ``<body>`` in the response might not necessarily be appropriate for all
    use cases. Please refer to the `Selenium FAQ`_ and
    `Selenium documentation`_ for more information.

    .. _Selenium FAQ: http://code.google.com/p/selenium/wiki/FrequentlyAskedQuestions#Q:_WebDriver_fails_to_find_elements_/_Does_not_block_on_page_loa
    .. _Selenium documentation: http://seleniumhq.org/docs/04_webdriver_advanced.html#explicit-waits

Test cases features
-------------------

Default test client
~~~~~~~~~~~~~~~~~~~

.. attribute:: SimpleTestCase.client

Every test case in a ``django.test.*TestCase`` instance has access to an
instance of a Django test client. This client can be accessed as
``self.client``. This client is recreated for each test, so you don't have to
worry about state (such as cookies) carrying over from one test to another.

This means, instead of instantiating a ``Client`` in each test::

    import unittest
    from django.test import Client

    class SimpleTest(unittest.TestCase):
        def test_details(self):
            client = Client()
            response = client.get('/customer/details/')
            self.assertEqual(response.status_code, 200)

        def test_index(self):
            client = Client()
            response = client.get('/customer/index/')
            self.assertEqual(response.status_code, 200)

...you can just refer to ``self.client``, like so::

    from django.test import TestCase

    class SimpleTest(TestCase):
        def test_details(self):
            response = self.client.get('/customer/details/')
            self.assertEqual(response.status_code, 200)

        def test_index(self):
            response = self.client.get('/customer/index/')
            self.assertEqual(response.status_code, 200)

Customizing the test client
~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. attribute:: SimpleTestCase.client_class

If you want to use a different ``Client`` class (for example, a subclass
with customized behavior), use the :attr:`~SimpleTestCase.client_class` class
attribute::

    from django.test import TestCase, Client

    class MyTestClient(Client):
        # Specialized methods for your environment...

    class MyTest(TestCase):
        client_class = MyTestClient

        def test_my_stuff(self):
            # Here self.client is an instance of MyTestClient...
            call_some_test_code()

.. _topics-testing-fixtures:

Fixture loading
~~~~~~~~~~~~~~~

.. attribute:: TransactionTestCase.fixtures

A test case for a database-backed Web site isn't much use if there isn't any
data in the database. To make it easy to put test data into the database,
Django's custom ``TransactionTestCase`` class provides a way of loading
**fixtures**.

A fixture is a collection of data that Django knows how to import into a
database. For example, if your site has user accounts, you might set up a
fixture of fake user accounts in order to populate your database during tests.

The most straightforward way of creating a fixture is to use the
:djadmin:`manage.py dumpdata <dumpdata>` command. This assumes you
already have some data in your database. See the :djadmin:`dumpdata
documentation<dumpdata>` for more details.

.. note::

    If you've ever run :djadmin:`manage.py migrate<migrate>`, you've
    already used a fixture without even knowing it! When you call
    :djadmin:`migrate` in the database for the first time, Django
    installs a fixture called ``initial_data``. This gives you a way
    of populating a new database with any initial data, such as a
    default set of categories.

    Fixtures with other names can always be installed manually using
    the :djadmin:`manage.py loaddata<loaddata>` command.

.. admonition:: Initial SQL data and testing

    Django provides a second way to insert initial data into models --
    the :ref:`custom SQL hook <initial-sql>`. However, this technique
    *cannot* be used to provide initial data for testing purposes.
    Django's test framework flushes the contents of the test database
    after each test; as a result, any data added using the custom SQL
    hook will be lost.

Once you've created a fixture and placed it in a ``fixtures`` directory in one
of your :setting:`INSTALLED_APPS`, you can use it in your unit tests by
specifying a ``fixtures`` class attribute on your :class:`django.test.TestCase`
subclass::

    from django.test import TestCase
    from myapp.models import Animal

    class AnimalTestCase(TestCase):
        fixtures = ['mammals.json', 'birds']

        def setUp(self):
            # Test definitions as before.
            call_setup_methods()

        def testFluffyAnimals(self):
            # A test that uses the fixtures.
            call_some_test_code()

Here's specifically what will happen:

* At the start of each test case, before ``setUp()`` is run, Django will
  flush the database, returning the database to the state it was in
  directly after :djadmin:`migrate` was called.

* Then, all the named fixtures are installed. In this example, Django will
  install any JSON fixture named ``mammals``, followed by any fixture named
  ``birds``. See the :djadmin:`loaddata` documentation for more
  details on defining and installing fixtures.

This flush/load procedure is repeated for each test in the test case, so you
can be certain that the outcome of a test will not be affected by another test,
or by the order of test execution.

By default, fixtures are only loaded into the ``default`` database. If you are
using multiple databases and set :attr:`multi_db=True
<TransactionTestCase.multi_db>`, fixtures will be loaded into all databases.

URLconf configuration
~~~~~~~~~~~~~~~~~~~~~

.. attribute:: SimpleTestCase.urls

If your application provides views, you may want to include tests that use the
test client to exercise those views. However, an end user is free to deploy the
views in your application at any URL of their choosing. This means that your
tests can't rely upon the fact that your views will be available at a
particular URL.

In order to provide a reliable URL space for your test,
``django.test.*TestCase`` classes provide the ability to customize the URLconf
configuration for the duration of the execution of a test suite. If your
``*TestCase`` instance defines an ``urls`` attribute, the ``*TestCase`` will use
the value of that attribute as the :setting:`ROOT_URLCONF` for the duration
of that test.

For example::

    from django.test import TestCase

    class TestMyViews(TestCase):
        urls = 'myapp.test_urls'

        def testIndexPageView(self):
            # Here you'd test your view using ``Client``.
            call_some_test_code()

This test case will use the contents of ``myapp.test_urls`` as the
URLconf for the duration of the test case.

.. _emptying-test-outbox:

Multi-database support
~~~~~~~~~~~~~~~~~~~~~~

.. attribute:: TransactionTestCase.multi_db

Django sets up a test database corresponding to every database that is
defined in the :setting:`DATABASES` definition in your settings
file. However, a big part of the time taken to run a Django TestCase
is consumed by the call to ``flush`` that ensures that you have a
clean database at the start of each test run. If you have multiple
databases, multiple flushes are required (one for each database),
which can be a time consuming activity -- especially if your tests
don't need to test multi-database activity.

As an optimization, Django only flushes the ``default`` database at
the start of each test run. If your setup contains multiple databases,
and you have a test that requires every database to be clean, you can
use the ``multi_db`` attribute on the test suite to request a full
flush.

For example::

    class TestMyViews(TestCase):
        multi_db = True

        def testIndexPageView(self):
            call_some_test_code()

This test case will flush *all* the test databases before running
``testIndexPageView``.

The ``multi_db`` flag also affects into which databases the
attr:`TransactionTestCase.fixtures` are loaded. By default (when
``multi_db=False``), fixtures are only loaded into the ``default`` database.
If ``multi_db=True``, fixtures are loaded into all databases.

.. _overriding-settings:

Overriding settings
~~~~~~~~~~~~~~~~~~~

.. method:: SimpleTestCase.settings

For testing purposes it's often useful to change a setting temporarily and
revert to the original value after running the testing code. For this use case
Django provides a standard Python context manager (see :pep:`343`) called
:meth:`~django.test.SimpleTestCase.settings`, which can be used like this::

    from django.test import TestCase

    class LoginTestCase(TestCase):

        def test_login(self):

            # First check for the default behavior
            response = self.client.get('/sekrit/')
            self.assertRedirects(response, '/accounts/login/?next=/sekrit/')

            # Then override the LOGIN_URL setting
            with self.settings(LOGIN_URL='/other/login/'):
                response = self.client.get('/sekrit/')
                self.assertRedirects(response, '/other/login/?next=/sekrit/')

This example will override the :setting:`LOGIN_URL` setting for the code
in the ``with`` block and reset its value to the previous state afterwards.

.. method:: SimpleTestCase.modify_settings

.. versionadded:: 1.7

It can prove unwieldy to redefine settings that contain a list of values. In
practice, adding or removing values is often sufficient. The
:meth:`~django.test.SimpleTestCase.modify_settings` context manager makes it
easy::

    from django.test import TestCase

    class MiddlewareTestCase(TestCase):

        def test_cache_middleware(self):
            with self.modify_settings(MIDDLEWARE_CLASSES={
                'append': 'django.middleware.cache.FetchFromCacheMiddleware',
                'prepend': 'django.middleware.cache.UpdateCacheMiddleware',
                'remove': [
                    'django.contrib.sessions.middleware.SessionMiddleware',
                    'django.contrib.auth.middleware.AuthenticationMiddleware',
                    'django.contrib.messages.middleware.MessageMiddleware',
                ],
            }):
                response = self.client.get('/')
                # ...

For each action, you can supply either a list of values or a string. When the
value already exists in the list, ``append`` and ``prepend`` have no effect;
neither does ``remove`` when the value doesn't exist.

.. function:: override_settings

In case you want to override a setting for a test method, Django provides the
:func:`~django.test.override_settings` decorator (see :pep:`318`). It's used
like this::

    from django.test import TestCase, override_settings

    class LoginTestCase(TestCase):

        @override_settings(LOGIN_URL='/other/login/')
        def test_login(self):
            response = self.client.get('/sekrit/')
            self.assertRedirects(response, '/other/login/?next=/sekrit/')

The decorator can also be applied to :class:`~django.test.TestCase` classes::

    from django.test import TestCase, override_settings

    @override_settings(LOGIN_URL='/other/login/')
    class LoginTestCase(TestCase):

        def test_login(self):
            response = self.client.get('/sekrit/')
            self.assertRedirects(response, '/other/login/?next=/sekrit/')

.. versionchanged:: 1.7

    Previously, ``override_settings`` was imported from ``django.test.utils``.

.. function:: modify_settings

.. versionadded:: 1.7

Likewise, Django provides the :func:`~django.test.modify_settings`
decorator::

    from django.test import TestCase, modify_settings

    class MiddlewareTestCase(TestCase):

        @modify_settings(MIDDLEWARE_CLASSES={
            'append': 'django.middleware.cache.FetchFromCacheMiddleware',
            'prepend': 'django.middleware.cache.UpdateCacheMiddleware',
        })
        def test_cache_middleware(self):
            response = self.client.get('/')
            # ...

The decorator can also be applied to test case classes::

    from django.test import TestCase, modify_settings

    @modify_settings(MIDDLEWARE_CLASSES={
        'append': 'django.middleware.cache.FetchFromCacheMiddleware',
        'prepend': 'django.middleware.cache.UpdateCacheMiddleware',
    })
    class MiddlewareTestCase(TestCase):

        def test_cache_middleware(self):
            response = self.client.get('/')
            # ...

.. note::

    When given a class, these decorators modify the class directly and return
    it; they don't create and return a modified copy of it. So if you try to
    tweak the above examples to assign the return value to a different name
    than ``LoginTestCase`` or ``MiddlewareTestCase``, you may be surprised to
    find that the original test case classes are still equally affected by the
    decorator. For a given class, :func:`~django.test.modify_settings` is
    always applied after :func:`~django.test.override_settings`.

.. warning::

    The settings file contains some settings that are only consulted during
    initialization of Django internals. If you change them with
    ``override_settings``, the setting is changed if you access it via the
    ``django.conf.settings`` module, however, Django's internals access it
    differently. Effectively, using :func:`~django.test.override_settings` or
    :func:`~django.test.modify_settings` with these settings is probably not
    going to do what you expect it to do.

    We do not recommend altering the :setting:`DATABASES` setting. Altering
    the :setting:`CACHES` setting is possible, but a bit tricky if you are
    using internals that make using of caching, like
    :mod:`django.contrib.sessions`. For example, you will have to reinitialize
    the session backend in a test that uses cached sessions and overrides
    :setting:`CACHES`.

You can also simulate the absence of a setting by deleting it after settings
have been overridden, like this::

    @override_settings()
    def test_something(self):
        del settings.LOGIN_URL
        ...

When overriding settings, make sure to handle the cases in which your app's
code uses a cache or similar feature that retains state even if the setting is
changed. Django provides the :data:`django.test.signals.setting_changed`
signal that lets you register callbacks to clean up and otherwise reset state
when settings are changed.

Django itself uses this signal to reset various data:

================================ ========================
Overridden settings              Data reset
================================ ========================
USE_TZ, TIME_ZONE                Databases timezone
TEMPLATE_CONTEXT_PROCESSORS      Context processors cache
TEMPLATE_LOADERS                 Template loaders cache
SERIALIZATION_MODULES            Serializers cache
LOCALE_PATHS, LANGUAGE_CODE      Default translation and loaded translations
MEDIA_ROOT, DEFAULT_FILE_STORAGE Default file storage
================================ ========================

Emptying the test outbox
~~~~~~~~~~~~~~~~~~~~~~~~

If you use any of Django's custom ``TestCase`` classes, the test runner will
clear the contents of the test email outbox at the start of each test case.

For more detail on email services during tests, see `Email services`_ below.

.. _assertions:

Assertions
~~~~~~~~~~

As Python's normal :class:`unittest.TestCase` class implements assertion methods
such as :meth:`~unittest.TestCase.assertTrue` and
:meth:`~unittest.TestCase.assertEqual`, Django's custom :class:`TestCase` class
provides a number of custom assertion methods that are useful for testing Web
applications:

The failure messages given by most of these assertion methods can be customized
with the ``msg_prefix`` argument. This string will be prefixed to any failure
message generated by the assertion. This allows you to provide additional
details that may help you to identify the location and cause of an failure in
your test suite.

.. method:: SimpleTestCase.assertRaisesMessage(expected_exception, expected_message, callable_obj=None, *args, **kwargs)

    Asserts that execution of callable ``callable_obj`` raised the
    ``expected_exception`` exception and that such exception has an
    ``expected_message`` representation. Any other outcome is reported as a
    failure. Similar to unittest's :meth:`~unittest.TestCase.assertRaisesRegexp`
    with the difference that ``expected_message`` isn't a regular expression.

.. method:: SimpleTestCase.assertFieldOutput(self, fieldclass, valid, invalid, field_args=None, field_kwargs=None, empty_value=u'')

    Asserts that a form field behaves correctly with various inputs.

    :param fieldclass: the class of the field to be tested.
    :param valid: a dictionary mapping valid inputs to their expected cleaned
        values.
    :param invalid: a dictionary mapping invalid inputs to one or more raised
        error messages.
    :param field_args: the args passed to instantiate the field.
    :param field_kwargs: the kwargs passed to instantiate the field.
    :param empty_value: the expected clean output for inputs in ``empty_values``.

    For example, the following code tests that an ``EmailField`` accepts
    "a@a.com" as a valid email address, but rejects "aaa" with a reasonable
    error message::

        self.assertFieldOutput(EmailField, {'a@a.com': 'a@a.com'}, {'aaa': [u'Enter a valid email address.']})

.. method:: SimpleTestCase.assertFormError(response, form, field, errors, msg_prefix='')

    Asserts that a field on a form raises the provided list of errors when
    rendered on the form.

    ``form`` is the name the ``Form`` instance was given in the template
    context.

    ``field`` is the name of the field on the form to check. If ``field``
    has a value of ``None``, non-field errors (errors you can access via
    ``form.non_field_errors()``) will be checked.

    ``errors`` is an error string, or a list of error strings, that are
    expected as a result of form validation.

.. method:: SimpleTestCase.assertFormsetError(response, formset, form_index, field, errors, msg_prefix='')

    .. versionadded:: 1.6

    Asserts that the ``formset`` raises the provided list of errors when
    rendered.

    ``formset`` is the name the ``Formset`` instance was given in the template
    context.

    ``form_index`` is the number of the form within the ``Formset``.  If
    ``form_index`` has a value of ``None``, non-form errors (errors you can
    access via ``formset.non_form_errors()``) will be checked.

    ``field`` is the name of the field on the form to check. If ``field``
    has a value of ``None``, non-field errors (errors you can access via
    ``form.non_field_errors()``) will be checked.

    ``errors`` is an error string, or a list of error strings, that are
    expected as a result of form validation.

.. method:: SimpleTestCase.assertContains(response, text, count=None, status_code=200, msg_prefix='', html=False)

    Asserts that a ``Response`` instance produced the given ``status_code`` and
    that ``text`` appears in the content of the response. If ``count`` is
    provided, ``text`` must occur exactly ``count`` times in the response.

    Set ``html`` to ``True`` to handle ``text`` as HTML. The comparison with
    the response content will be based on HTML semantics instead of
    character-by-character equality. Whitespace is ignored in most cases,
    attribute ordering is not significant. See
    :meth:`~SimpleTestCase.assertHTMLEqual` for more details.

.. method:: SimpleTestCase.assertNotContains(response, text, status_code=200, msg_prefix='', html=False)

    Asserts that a ``Response`` instance produced the given ``status_code`` and
    that ``text`` does not appears in the content of the response.

    Set ``html`` to ``True`` to handle ``text`` as HTML. The comparison with
    the response content will be based on HTML semantics instead of
    character-by-character equality. Whitespace is ignored in most cases,
    attribute ordering is not significant. See
    :meth:`~SimpleTestCase.assertHTMLEqual` for more details.

.. method:: SimpleTestCase.assertTemplateUsed(response, template_name, msg_prefix='')

    Asserts that the template with the given name was used in rendering the
    response.

    The name is a string such as ``'admin/index.html'``.

    You can use this as a context manager, like this::

        with self.assertTemplateUsed('index.html'):
            render_to_string('index.html')
        with self.assertTemplateUsed(template_name='index.html'):
            render_to_string('index.html')

.. method:: SimpleTestCase.assertTemplateNotUsed(response, template_name, msg_prefix='')

    Asserts that the template with the given name was *not* used in rendering
    the response.

    You can use this as a context manager in the same way as
    :meth:`~SimpleTestCase.assertTemplateUsed`.

.. method:: SimpleTestCase.assertRedirects(response, expected_url, status_code=302, target_status_code=200, msg_prefix='', fetch_redirect_response=True)

    Asserts that the response return a ``status_code`` redirect status, it
    redirected to ``expected_url`` (including any GET data), and the final
    page was received with ``target_status_code``.

    If your request used the ``follow`` argument, the ``expected_url`` and
    ``target_status_code`` will be the url and status code for the final
    point of the redirect chain.

    .. versionadded:: 1.7

    If ``fetch_redirect_response`` is ``False``, the final page won't be
    loaded. Since the test client can't fetch externals URLs, this is
    particularly useful if ``expected_url`` isn't part of your Django app.

    .. versionadded:: 1.7

    Scheme is handled correctly when making comparisons between two URLs. If
    there isn't any scheme specified in the location where we are redirected to,
    the original request's scheme is used. If present, the scheme in
    ``expected_url`` is the one used to make the comparisons to.

.. method:: SimpleTestCase.assertHTMLEqual(html1, html2, msg=None)

    Asserts that the strings ``html1`` and ``html2`` are equal. The comparison
    is based on HTML semantics. The comparison takes following things into
    account:

    * Whitespace before and after HTML tags is ignored.
    * All types of whitespace are considered equivalent.
    * All open tags are closed implicitly, e.g. when a surrounding tag is
      closed or the HTML document ends.
    * Empty tags are equivalent to their self-closing version.
    * The ordering of attributes of an HTML element is not significant.
    * Attributes without an argument are equal to attributes that equal in
      name and value (see the examples).

    The following examples are valid tests and don't raise any
    ``AssertionError``::

        self.assertHTMLEqual('<p>Hello <b>world!</p>',
            '''<p>
                Hello   <b>world! <b/>
            </p>''')
        self.assertHTMLEqual(
            '<input type="checkbox" checked="checked" id="id_accept_terms" />',
            '<input id="id_accept_terms" type='checkbox' checked>')

    ``html1`` and ``html2`` must be valid HTML. An ``AssertionError`` will be
    raised if one of them cannot be parsed.

    Output in case of error can be customized with the ``msg`` argument.

.. method:: SimpleTestCase.assertHTMLNotEqual(html1, html2, msg=None)

    Asserts that the strings ``html1`` and ``html2`` are *not* equal. The
    comparison is based on HTML semantics. See
    :meth:`~SimpleTestCase.assertHTMLEqual` for details.

    ``html1`` and ``html2`` must be valid HTML. An ``AssertionError`` will be
    raised if one of them cannot be parsed.

    Output in case of error can be customized with the ``msg`` argument.

.. method:: SimpleTestCase.assertXMLEqual(xml1, xml2, msg=None)

    Asserts that the strings ``xml1`` and ``xml2`` are equal. The
    comparison is based on XML semantics. Similarly to
    :meth:`~SimpleTestCase.assertHTMLEqual`, the comparison is
    made on parsed content, hence only semantic differences are considered, not
    syntax differences. When unvalid XML is passed in any parameter, an
    ``AssertionError`` is always raised, even if both string are identical.

    Output in case of error can be customized with the ``msg`` argument.

.. method:: SimpleTestCase.assertXMLNotEqual(xml1, xml2, msg=None)

    Asserts that the strings ``xml1`` and ``xml2`` are *not* equal. The
    comparison is based on XML semantics. See
    :meth:`~SimpleTestCase.assertXMLEqual` for details.

    Output in case of error can be customized with the ``msg`` argument.

.. method:: SimpleTestCase.assertInHTML(needle, haystack, count=None, msg_prefix='')

    Asserts that the HTML fragment ``needle`` is contained in the ``haystack`` one.

    If the ``count`` integer argument is specified, then additionally the number
    of ``needle`` occurrences will be strictly verified.

    Whitespace in most cases is ignored, and attribute ordering is not
    significant. The passed-in arguments must be valid HTML.

.. method:: SimpleTestCase.assertJSONEqual(raw, expected_data, msg=None)

    Asserts that the JSON fragments ``raw`` and ``expected_data`` are equal.
    Usual JSON non-significant whitespace rules apply as the heavyweight is
    delegated to the :mod:`json` library.

    Output in case of error can be customized with the ``msg`` argument.

.. method:: TransactionTestCase.assertQuerysetEqual(qs, values, transform=repr, ordered=True)

    Asserts that a queryset ``qs`` returns a particular list of values ``values``.

    The comparison of the contents of ``qs`` and ``values`` is performed using
    the function ``transform``; by default, this means that the ``repr()`` of
    each value is compared. Any other callable can be used if ``repr()`` doesn't
    provide a unique or helpful comparison.

    By default, the comparison is also ordering dependent. If ``qs`` doesn't
    provide an implicit ordering, you can set the ``ordered`` parameter to
    ``False``, which turns the comparison into a Python set comparison.

    .. versionchanged:: 1.6

        The method now checks for undefined order and raises ``ValueError``
        if undefined order is spotted. The ordering is seen as undefined if
        the given ``qs`` isn't ordered and the comparison is against more
        than one ordered values.

.. method:: TransactionTestCase.assertNumQueries(num, func, *args, **kwargs)

    Asserts that when ``func`` is called with ``*args`` and ``**kwargs`` that
    ``num`` database queries are executed.

    If a ``"using"`` key is present in ``kwargs`` it is used as the database
    alias for which to check the number of queries.  If you wish to call a
    function with a ``using`` parameter you can do it by wrapping the call with
    a ``lambda`` to add an extra parameter::

        self.assertNumQueries(7, lambda: my_function(using=7))

    You can also use this as a context manager::

        with self.assertNumQueries(2):
            Person.objects.create(name="Aaron")
            Person.objects.create(name="Daniel")

.. _topics-testing-email:

Email services
--------------

If any of your Django views send email using :doc:`Django's email
functionality </topics/email>`, you probably don't want to send email each time
you run a test using that view. For this reason, Django's test runner
automatically redirects all Django-sent email to a dummy outbox. This lets you
test every aspect of sending email -- from the number of messages sent to the
contents of each message -- without actually sending the messages.

The test runner accomplishes this by transparently replacing the normal
email backend with a testing backend.
(Don't worry -- this has no effect on any other email senders outside of
Django, such as your machine's mail server, if you're running one.)

.. currentmodule:: django.core.mail

.. data:: django.core.mail.outbox

During test running, each outgoing email is saved in
``django.core.mail.outbox``. This is a simple list of all
:class:`~django.core.mail.EmailMessage` instances that have been sent.
The ``outbox`` attribute is a special attribute that is created *only* when
the ``locmem`` email backend is used. It doesn't normally exist as part of the
:mod:`django.core.mail` module and you can't import it directly. The code
below shows how to access this attribute correctly.

Here's an example test that examines ``django.core.mail.outbox`` for length
and contents::

    from django.core import mail
    from django.test import TestCase

    class EmailTest(TestCase):
        def test_send_email(self):
            # Send message.
            mail.send_mail('Subject here', 'Here is the message.',
                'from@example.com', ['to@example.com'],
                fail_silently=False)

            # Test that one message has been sent.
            self.assertEqual(len(mail.outbox), 1)

            # Verify that the subject of the first message is correct.
            self.assertEqual(mail.outbox[0].subject, 'Subject here')

As noted :ref:`previously <emptying-test-outbox>`, the test outbox is emptied
at the start of every test in a Django ``*TestCase``. To empty the outbox
manually, assign the empty list to ``mail.outbox``::

    from django.core import mail

    # Empty the test outbox
    mail.outbox = []

.. _skipping-tests:

Skipping tests
--------------

.. currentmodule:: django.test

The unittest library provides the :func:`@skipIf <unittest.skipIf>` and
:func:`@skipUnless <unittest.skipUnless>` decorators to allow you to skip tests
if you know ahead of time that those tests are going to fail under certain
conditions.

For example, if your test requires a particular optional library in order to
succeed, you could decorate the test case with :func:`@skipIf
<unittest.skipIf>`. Then, the test runner will report that the test wasn't
executed and why, instead of failing the test or omitting the test altogether.

To supplement these test skipping behaviors, Django provides two
additional skip decorators. Instead of testing a generic boolean,
these decorators check the capabilities of the database, and skip the
test if the database doesn't support a specific named feature.

The decorators use a string identifier to describe database features.
This string corresponds to attributes of the database connection
features class. See ``django.db.backends.BaseDatabaseFeatures``
class for a full list of database features that can be used as a basis
for skipping tests.

.. function:: skipIfDBFeature(feature_name_string)

Skip the decorated test or ``TestCase`` if the named database feature is
supported.

For example, the following test will not be executed if the database
supports transactions (e.g., it would *not* run under PostgreSQL, but
it would under MySQL with MyISAM tables)::

    class MyTests(TestCase):
        @skipIfDBFeature('supports_transactions')
        def test_transaction_behavior(self):
            # ... conditional test code

.. versionchanged:: 1.7

    ``skipIfDBFeature`` can now be used to decorate a ``TestCase`` class.

.. function:: skipUnlessDBFeature(feature_name_string)

Skip the decorated test or ``TestCase`` if the named database feature is *not*
supported.

For example, the following test will only be executed if the database
supports transactions (e.g., it would run under PostgreSQL, but *not*
under MySQL with MyISAM tables)::

    class MyTests(TestCase):
        @skipUnlessDBFeature('supports_transactions')
        def test_transaction_behavior(self):
            # ... conditional test code

.. versionchanged:: 1.7

    ``skipUnlessDBFeature`` can now be used to decorate a ``TestCase`` class.